SUMMARY PARAGRAPH for PEX19
The biogenesis of peroxisomes requires a group of protein factors referred to as peroxins which are encoded by the PEX genes. Peroxisomal proteins are synthesized on free polyribosomes and imported posttranslationally. The transport of peroxisomal matrix proteins from the cytoplasm to the peroxisome is mediated by two peroxisome-targeting signal sequences (PTS1 and PTS2). Peroxisomal membrane proteins (PMPs) are imported independently of the matrix proteins by a distinct mechanism mediated by the membrane PTS signal (mPTS) (2, 5, 6, 7 and references therein).
In yeast, Pex19p and Pex3p are two proteins required for the proper localization and stability of PMPs (2). Pex19p is a farnesylated, hydrophilic and acidic protein that has chaperone and receptor functions (1, 7). It binds and stabilizes newly synthesized class I peroxisomal membrane proteins (PMPs) in the cytoplasm and delivers them to the peroxisome for subsequent insertion into the peroxisome membrane (8, 7 and references there in). Pex19p interacts with Pex3p in the ER during the early stages of de novo peroxisome biogenesis and is required for the exit of Pex3p from the ER (9, 10, 11). pex19 null mutants completely lack detectable peroxisomal membrane structures and mislocalize the PMPs to the cytosol where they are rapidly degraded (2).
Pex19p is evolutionarily conserved, and shares sequence similarity with human Pex19p (also known as PXF). The human peroxisome biogenesis disorders (PBDs) are a group of genetically heterogeneous diseases characterized by severe mental retardation, neuronal, hepatic and renal abnormalities, and death in early infancy (12). Mutations in human PEX19 have been associated with Zellweger Syndrome and Refsum Disease.
Last updated: 2007-07-05